When sending digital video data, compression of the digital video data is used for reducing the bit rate of the digital video data.
The bit rate may be controlled by setting a predetermined constant bit rate. This will result in that parts of the digital video data where the degree of detail and/or motion in the captured scene is relatively low will risk being compressed in an unnecessarily small degree, resulting in that the compressed digital video data is taking up unnecessarily high amounts of bandwidth and/or storage space. Moreover, this will also result in that parts of the digital video data where the degree of detail and/or motion in the captured scene is relatively high will risk being compressed in a too large degree, resulting in that the image quality of the compressed digital video data is compromised.
Alternatively, the bit rate may be controlled by setting a maximum bit rate used for keeping the bit rate close to or below the predetermined maximum. The predetermined maximum is implemented as a fixed parameter in a bit rate controller. A relatively high predetermined maximum bit rate may require a large bandwidth and/or storage for the digital video data, whereas a relatively low predetermined maximum bit rate will risk compromising the image quality of the digital video data when there is a lot of detail or motion in the captured scene.
Yet alternatively, the bit rate controller may employ variable bit rate, which may also be referred to as constant quality, where the bit rate is allowed to vary in order to maintain a certain image quality. This may lead to a too high usage of bandwidth when there is a lot of detail or motion in the scene. Moreover, this may lead to a very high bit rate at low light conditions capturing the digital video data. A high gain on the signal from the image sensor will be needed for capturing the digital video data in low light conditions. This will result in a lot of noise in the digital video data, which requires large amounts of bits for encoding.